Conventional waste heat treatment devices include batch furnaces in which wastes are burned intermittently, and continuous feed incinerators in which wastes are successively moved in the furnace by means of a belt so that the wastes are burned continuously. In either type of the incinerators, wastes are burned and disposed by the heat of burning gas fuel or liquid fuel in a burner. These conventional waste incinerators are advantageous in that many different wastes can be treated at one time. Conversely, since a large volume of waste is burned at one time and a burner is used, the incinerators inevitably have a complicated structure and a large size, which leads to higher installation costs.
In addition, since it is large, conventional devices of this type are very difficult to move conventional heat treatment devices, and it is hard to install these devices close to where such wastes are generated. The wastes must be transported to a distant incinerator. Where the materials to be treated include medical wastes and the location where such wastes are produced is far from the incinerator, it has been pointed out that persons who treat the medical waste may possibly be infected by pathogenic bacteria or the like included in the medical waste while transporting the medical waste to the incinerator.
An incinerator which burns various wastes indirectly by microwave and makes the wastes harmless by radiating microwave into the burning gas generated by burning has been proposed, for example, in Japanese Patent Laying -Open No. 64-58910, as another example of the conventional waste heat treatment apparatus which does not use a burner for burning the waste.
Referring to FIG. 1, the waste incinerator proposed in the aforementioned patent application includes a combustion chamber 1 divided into a primary combustion chamber 3 and a secondary combustion chamber 4 by a microwave attenuating portion 2. A waste carrier 5 is provided in the primary combustion chamber 3. A microwave heater 6 is provided on a side surface of the waste carrier 5. The primary combustion chamber 3 is connected to a magnetron 7 by means of a waveguide 8 with a microwave transmitting body 9 provided at the connection between the primary combustion chamber 3 and the waveguide 8. Thus the burning gas is prevented from entering the waveguide 8, thereby protecting the magnetron 7. A plurality of primary air inlets 10 are provided in the primary combustion chamber 3.
A plurality of secondary air inlets 11 and an igniter 12 are provided in the secondary combustion chamber 4 so as to ignite and burn the inflammable gas fed from the primary combustion chamber 3 into the secondary combustion chamber 4. On the downstream side of the secondary combustion chamber 4, a catalyzer chamber 13 is provided. A catalyzer 14 and a filter 15 are contained in the chamber 13. The catalyzer 14 is kept at a temperature that maintains the catalyzer is maintained, by means of a catalyzer heater 16. The burning gas is purified by the catalyzer 14 and the filter 15 and exhausted through an exhaust tube 17.
The operation of the conventional microwave type waste incinerator having the above described structure is as follows. When waste 20 introduced through an outer door 18 and an inner door 19 and placed on the waste carrier 5, is irradiated with microwave, the microwave energy is entirely absorbed by the waste 20, the water in the waste 20 is evaporated, and the waste 20 is dried quickly. After the waste 20 is fully dried the microwave energy begins to heat the microwave heater 6. The temperature of the microwave heater 6 gradually increases, and the heater heats the waste 20 which is in contact with the microwave heater 6 thereby promoting carbonization of the waste 20 while generating inflammable gases from the waste 20. The inflammable gases generated from the waste and the dried waste itself are ignited and burned by discharge of heat into the carbonized waste 20 or by the inginter 12 provided in the secondary combustion chamber 4.
The above described waste incinerator utilizing microwave has the following problems.
First, the temperature control for the burning is difficult in the incinerators utilizing high frequency or microwave energy, causing malfunctions. Further, the generated microwave energy may adversely affect, the control mechanism of the incinerator itself resulting in a malfunction, or instruments of other devices may be adversely affected by the microwave energy.